linux-kernel - Re: [PATCH v5 07/10] Drivers: hv: Introduce per-cpu event ring tail

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Message-ID: <Z7-mG7X-cyZAKa7V@skinsburskii.>
Date: Wed, 26 Feb 2025 15:39:07 -0800
From: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
To: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
Cc: linux-hyperv@...r.kernel.org, x86@...nel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org, linux-acpi@...r.kernel.org,
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	Tianyu.Lan@...rosoft.com, stanislav.kinsburskiy@...il.com,
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	anrayabh@...ux.microsoft.com, rafael@...nel.org, lenb@...nel.org,
	corbet@....net
Subject: Re: [PATCH v5 07/10] Drivers: hv: Introduce per-cpu event ring tail

On Wed, Feb 26, 2025 at 03:08:01PM -0800, Nuno Das Neves wrote:
> Add a pointer hv_synic_eventring_tail to track the tail pointer for the
> SynIC event ring buffer for each SINT.
> 
> This will be used by the mshv driver, but must be tracked independently
> since the driver module could be removed and re-inserted.
> 
> Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
> Reviewed-by: Wei Liu <wei.liu@...nel.org>
> ---
>  drivers/hv/hv_common.c | 34 ++++++++++++++++++++++++++++++++--
>  1 file changed, 32 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index 252fd66ad4db..2763cb6d3678 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -460,6 +478,7 @@ void __init ms_hyperv_late_init(void)
>  int hv_common_cpu_init(unsigned int cpu)
>  {
>  	void **inputarg, **outputarg;
> +	u8 **synic_eventring_tail;
>  	u64 msr_vp_index;
>  	gfp_t flags;
>  	const int pgcount = hv_output_page_exists() ? 2 : 1;
> @@ -472,8 +491,8 @@ int hv_common_cpu_init(unsigned int cpu)
>  	inputarg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
>  
>  	/*
> -	 * hyperv_pcpu_input_arg and hyperv_pcpu_output_arg memory is already
> -	 * allocated if this CPU was previously online and then taken offline
> +	 * The per-cpu memory is already allocated if this CPU was previously
> +	 * online and then taken offline
>  	 */
>  	if (!*inputarg) {
>  		mem = kmalloc(pgcount * HV_HYP_PAGE_SIZE, flags);
> @@ -485,6 +504,17 @@ int hv_common_cpu_init(unsigned int cpu)
>  			*outputarg = (char *)mem + HV_HYP_PAGE_SIZE;
>  		}
>  
> +		if (hv_root_partition()) {
> +			synic_eventring_tail = (u8 **)this_cpu_ptr(hv_synic_eventring_tail);
> +			*synic_eventring_tail = kcalloc(HV_SYNIC_SINT_COUNT,
> +							sizeof(u8), flags);
> +

Redundant empty line ^^^
> +			if (unlikely(!*synic_eventring_tail)) {
> +				kfree(mem);
> +				return -ENOMEM;
> +			}
> +		}
> +
>  		if (!ms_hyperv.paravisor_present &&
>  		    (hv_isolation_type_snp() || hv_isolation_type_tdx())) {
>  			ret = set_memory_decrypted((unsigned long)mem, pgcount);

Reviewed-by: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>

> -- 
> 2.34.1
>